1. Technical Field
The present invention relates to optical transmission systems and more particularly to a polarization multiplexing system and method to increase system capacity in optical transmission systems.
2. Description of the Related Art
As the demand on capacity rapidly increases, spectral efficiency (SE) is becoming increasingly more important for high speed optical transmission systems. To achieve high SE, polarization multiplexing (PolMux) is a technology of interest since PolMux works well with any modulation format and can increase the spectral efficiency from the original SE of the modulation format without PolMux. PolMux requires changes to a transmitter side by adding the polarization beam combiner (PBC), and needs coherent detection as the only option at a receiver side. This results in a high complexity and has not been technically proven for practical systems.
In a coherent detection receiver, both frequency offset and phase offset need to be removed by digital processing which requires a large amount of power consumption and complicated system design. The coherent detection receiver also needs spare narrow line-width lasers at the receiver as a local oscillator which can increase both system cost and complexity.